Field of the Invention
The present invention relates to polypeptides having dextranase activity, and polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.
Description of the Related Art
Dextran (polysaccharide with high molecular weight and predominantly straight-chained glucose polymer with a majority of alpha-1-6 glucosidic linkages) is highly undesirable impurity causing severe processing problems in sugarcane mills and sugar beet mills as well as sugar refineries. The effects of the presence of dextran on sugar mill flow are numerous and varied (Imrie F K E, Tilbury R H. (1972). Polysaccharides in sugar cane and its products. Sugar Technology Reviews 1972; 1:291-361; Rauh J S, Cuddihy J A, Opelka M J. (1999). Analyzing Dextran in the Sugar Industry: A Review of Dextran in the Factory and a New Analytical Technique. 30th Biennial Meeting, American Society of Sugar Beet Technologists, 1999, Orlando, Fla., USA.; Eggleston, G, Monge A, Montes B, Stewart D (2009), Application of dextranases in sugarcane factory: Overcoming practical, Sugar Tech (2009) 11(2): 135-141), bringing about significant losses to the sugar industries: the raw sugar industry and the refined sugar industry. Dextran is formed irreversibly from the sucrose contained in the raw materials (Cuddihy J A, Rauh J S, Porro M E. (1998). Improving sugar recovery with sugar process chemicals. Midland Research Laboratories, Inc. 1998). The most significant impact of the dextran contamination is on the viscosity of sugar processing streams. Dextran in raw juices causes poor clarification since it acts as a protective colloid inhibiting the coagulation phase in the decanter (Ravno, A. B., and B. B. Purchase. 2006. Dealing with dextran in the South African sugar industry. International Sugar Journal 108:255-269). As a result, more color and ash are expected in the sugar made from such juice with fine suspended matter. Sugar refineries can face large challenges on the filtration rates leading to reduced throughput due to the presence of this suspended matter (Donavan, M, 1993, Raw sugar quality. The effect on the refiner. Proc. Sugar. Ind. Technol., 52, 117-130). The increased viscosity caused by the dextran in sugar processing streams interferes negatively on heat transfers rates, increases scale deposits on evaporators/heaters, lower molasses exhaustion and lower purging efficiency in centrifuges (Geronimos, G. L and P. F. Greenfield (1978). Viscosity increases in concentrated sugar solutions and molasses due to dextrans. In proceedings of the Queesland Society of Sugar Cane Technologist, 45th Conference, Quaeesland, Australia, 119-126; Singleton, V., Horn, J., Bucke, C. and Adlard, M. (2001): A new polarimetric method for the analysis of dextran and sucrose. International Sugar Journal, 103(1230), 251-254; Kim, D and Day D. F, (2004), Determination of dextran in raw sugar process streams, Food Science and Biotechnology, 13:248-252). The presence of dextran also influences the rate of crystallization and causes elongation of sugars crystals (Covacevich M T, Richards G N and G Stokie (1977). Studies on the effect of dextran structure on cane sugar crystal elongation and methods of analysis. In Proceedings of the XVI ISSCT Congress, Sao Paulo, S P, Brazil, 2493-2508) with severe drawbacks for the end chain factories of sugar (Vane G. W. (1981) The effect of dextran on the distortion of hard candy. Proc. Sugar Ind. Technol., 40, 95-102; Haynes, L Zhou L and Hopkins W (2004). Dextran in refined sugar: impact on hard candy processing. Proc. Sugar Proc Res Inst: 138-146)). Thus it can be concluded that the benefits resulting in removal of dextran include viscosity decrease leading to increased sugar recovery and also to improve sugar quality. In particular it is the high molecular mass dextran (>106 g/gmol) that has an impact on viscosity and handling properties of massecuites, and thus this is the type of dextran that needs to be targeted by the dextranase.
Dextranase is often added before the last evaporator when dextran levels are high, or in juice tanks.
Several commercial Dextranase products are available, e.g., Dextranase Plus L (Novozymes NS) which is a dextranase from Chaetomium erraticum. 
There is a need in the art for improved dextranase enzymes useful for reducing dextran content in sugar solutions in sugarcane mills, sugar beet mills as well as sugar refineries.
SWISSPROT:B2MW82 discloses a dextranase from Talaromyces pinophilus. 
The present invention provides polypeptides having dextranase activity and polynucleotides encoding the polypeptides.